The present invention generally relates to a method of searching for an end point (completion point) of a recorded data region (hereinafter referred to as a recorded data region end search method) of a recording medium in a recording and reproducing apparatus, particularly an S-DAT (e.g., a stationary head system digital audio tape recorder) having both forward and backward tape recording running directions, and to a method of recording data appended to an already recorded region on a recording medium (hereinafter referred to as a connecting data recording method), and to a method of recording control data to be used in the connecting data recording and recorded data region end search methods.
In a recording apparatus such as, for example, a compact cassette, an S-DAT and an R-DAT (rotary head system digital audio tape recorder), recording end point information to be read during normal reproduction and during a high speed search is recorded at the completion point of a recorded data region on the recording medium. This recording completion point information is used as a guide in a case where a new data region is to be recorded contiguous to the prior recorded region. The subsequent portion is not accessed by reference to the recording completion point information provided as a guide of the final point of the effective region on the magnetic tape, so that undesired data is not read by mistake. It is well known and recommended that a lead out area indicative of the trailing end of a recorded data region also be recorded. See page 89 to page 90 of the "THE DAT CONFERENCE STANDARD, DIGITAL AUDIO TAPE RECORDER SYSTEM" (DOCUMENT 1) issued by the DAT consultant conference in June, 1987. The reasons why the recording of the lead out area is necessary are as follows.
1. As a guide in the connecting data recording. PA1 2. As a guide of the completion point of an effective data region.
Particularly, the lead out area becomes necessary when overwriting prior recorded data in a case where a completion point of the prior recorded data region is after the completion point of a later recorded data region where the new signal has been recorded. The location of a completion point recorded data associated with the prior recorded data cannot be regarded as the completion point of the later recorded data.
Although it is possible to detect the completion point of the recorded data through detection of a non-recorded portion in the case of a first recording on a tape, the completion point of the recording may be detected more positively and more quickly if the lead out area is recorded. This is because it is necessary to confirm a non-recorded condition of a number of frames to positively detect the non-recorded position, instead of a burst error caused by drop out. Although the data completion point can be identified by the non-recorded portion, the completion point may be identified more immediately when a recorded lead out area is detected.
In, for example, the R-DAT, the lead out area is recorded for 300 frames or more. When the lead out area is detected during a recorded data region end search, the tape running operation is stopped and the tape is rewound several frames to enter a standby condition for the connecting data recording. The connecting data recording means effects recording so that the phase and so on of a frame is continuous with already recorded frames. The recording position of the already recorded frame must be confirmed so as to read the time record, the frame number and so on before the connecting data recording. Also, as the tape speed must be made constant before the start of recording, and the tape must be run for a period of several frames to achieve the necessary constant tape speed. Therefore, the rewinding operation is effected for several frames after the detection of the lead out area, and then a standby condition is entered.
A frame includes a plus azimuth track recorded by a plus azimuth head and a minus azimuth track recorded by the minus azimuth head in the case of the R-DAT. Hereinafter, a frame is a minimum unit which can be independently recorded and reproduced.
Also, a lead out area ID is recorded in a sub ID area of auxiliary data. The data to be used for control, such as the lead out area ID, is called auxiliary data, in contrast with the audio data and image data, for example, which is called main data.
The R-DAT is illustrated from pages 47 to 165 of "Graphical DAT Reader" (Document 2) issued Jul. 25, 1988 by OHM-Sha. Also, the S-DAT is explained from page 42 to page 46 of Document 2.
When the recording completion point is searched by the recording and reproducing apparatus of a fixed head system having a forward and backward tape running direction, such as a compact cassette and a S-DAT, using a lead out area ID as in the above described R-DAT, the following problems arise.
1. When a recorded data region end search is performed by a recording and reproducing apparatus having two tape running directions, there is no way of telling whether the lead out area of a certain plane (upper or lower region) of the tape is a recording completion point of the entire tape or a recording completion point of the plane only.
2. Since, when the recording period of the recording completion point information is short, the recording completion point information cannot be detected positively during a high speed search and there is a possibility of missing the recording completion point.
In the recording and reproducing apparatus of a fixed head system having tape running directions in both the forward direction and the backward direction, the magnetic tape is normally divided into an upper half region and a lower half region. The upper half of the magnetic tape may be used in, for example, the recording in the forward direction, and the lower half region may be used in the recording of the backward direction. The two recording regions are called respectively an A plane and a B plane. The B plane is a reverse plane with respect to the A plane and the A plane is a reverse plane with respect to the B plane.
The above described problem point 2 will be described hereinafter in further detail.
As the head crosses the recording track obliquely in the case of an R-DAT, the head speed is not changed in proportion to the tape speed, and the control data is not always read for every track. Thus, the lead out area of the R-DAT is determined to record continuously by 300 frames. Although the head does not obliquely cross the tracks in the case of the S-DAT, the bit rate of the reproduction signal changes in proportion to the changes in the tape speed, so that the bit rate changes considerably during the operation of increasing the tape speed and extraction of the reproduction clock is hard to effect, with a probability of reading the data correctly being reduced as compared with that of the normal reproduction time. Therefore, in the case of the S-DAT, the probability of missing the lead out area must be reduced by recording a lead out area having a longer recording period.